javascript
Pure JavaScript/TypeScript library for multiline text measurement & layout. Fast, accurate & supports all the languages you didn't even know about. Allows rendering to DOM, Canvas, SVG and soon, server-side.
Pretext side-steps the need for DOM measurements (e.g. getBoundingClientRect, offsetHeight), which trigger layout reflow, one of the most expensive operations in the browser. It implements its own text measurement logic, using the browsers' own font engine as ground truth (very AI-friendly iteration method).
Structure LLM Outputs with Ease. Structured outputs powered by LLMs.
The simplest way to extract structured data from LLMs with type safety and validation.
Get reliable JSON from any LLM. Built on Pydantic for validation, type safety, and IDE support.
A manifest of JS modules and their more modern/active replacements.
As part of the community e18e effort, this project provides a collection of module replacements (i.e. possible alternative packages).
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Open Source Video Player.
open source media player framework for Web and React. Modern, modular, and composable media player framework for Web and React.
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The first UI framework for the agentic era — tiny, performant, with WASM sandboxes for safe code execution.
A tiny, blazing-fast, zero dependency, type-safe framework with no build step required.
ArrowJS ships with the ability to isolate component logic inside Web Assembly sandboxes while rendering full inline DOM directly in your app — no iframes, no pre-defined UI components.
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Code and preview Word documents in the browser
A browser-based, client-side editor that helps you create .docx files using the JavaScript library Docx.js with live preview.
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High-Performance Data Grid for Vue, React, Angular, Svelte, and JavaScript. RevoGrid is a high-performance JavaScript Data Grid built for massive datasets. 60fps, 3x less memory
Haptic feedback for the mobile web. Supports React, Vue, and Svelte.
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🌳 Tiny & elegant JavaScript HTTP client based on the Fetch API.
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The AI Operator Living in Your Web Page. JavaScript in-page GUI agent. Control web interfaces with natural language.
🪄One line of code, turns your website into an AI-native app. Users give natural language commands, AI handles the rest.
Unified Security Platform from Code to Runtime.
Protect against malicious code installed via npm, yarn, pnpm, npx, and pnpx with Aikido Safe Chain. Free to use, no tokens required.
Full NumPy, in TypeScript/JavaScript (94% coverage).
The most comprehensive NumPy implementation for TypeScript and JavaScript. Write numerical computing code with the same API you already know from Python — fully type-safe, tree-shakeable, and validated against NumPy itself.
Production-Ready Full-Stack Framework.
CedarJS is a stable, opinionated full-stack framework that integrates React, GraphQL, and Prisma into a cohesive system. Don't waste weeks on boilerplate—use the foundation trusted for production-grade applications.
A fast, lightweight, and responsive masonry grid layout library.
Light Weight "Headroom Style" scroll intent library that hides the site header on scroll down and shows on scroll up.
A lightweight JavaScript library for creating smart header behavior based on scroll intent. Peek automatically hides your site header when users scroll down and reveals it when they scroll up, creating a more immersive browsing experience.
The Lightweight Reactive Library.
Minimal reactive state management using only standard JavaScript and HTML - no custom syntax, no build step required.
Minimal PDF creation library. <400 LOC, zero dependencies, makes real PDFs.
Super-configurable and well-tested web page minifier (enhanced successor of HTML Minifier).
Stop logging into a black hole. Give your logs a beautiful, powerful, and interactive home.
log-vwer is the ultimate plug-and-play toolkit for Node.js developers who are tired of messy console.log statements. It instantly gives you a professional-grade dashboard to view, search, and filter your application logs in real-time.
Slow down, pause, or speed up time of any web content.
Debug animations, study cool demos, and make games easier or harder.
The WebMCP API enables web applications to provide JavaScript-based tools to AI agents.
Related contents:
- Chrome’s WebMCP makes AI agents stop pretending @ Reading.sh's Medium.
- #127 - News Février 2026, du WebMCP, des agents spammeurs et du Markdown @ Double Slash :fr:.
- #1037: WebMCP is here (and you should care) @ Syntax.
- WebMCP: A Practical Guide to Agent-Ready Websites @ Freshman.
- Why WebMCP matters @ Yoav's blog thing.
- The next steps on the Web and WebMCP @ Unlocking The Agentic Web Economy.
Pretty logs in JavaScript!
Simple, powerful, and pretty. Make and improve your logs with kittylog.
KittyLog is a JavaScript library that makes your logs visually appealing and easy to understand. It helps organize information clearly and adds colors and styles to make messages stand out.
Simple and modern email sending library
Universal interface for emailing across runtimes.
Upyo is a simple and cross-runtime library for sending email messages using SMTP and various email providers. It works on Node.js, Deno, Bun, and edge functions.
Access the system clipboard (copy/paste).
Cross-platform. Supports: macOS, Windows, Linux (including Wayland), OpenBSD, FreeBSD, Android with Termux, and modern browsers.
La classe Vanilla JS universelle pour Google Maps.
MagixMaps est une bibliothèque JavaScript légère, performante et sans dépendances (Vanilla JS), conçue pour intégrer l'API Google Maps (version 2026) dans tout projet web.
API mocking library for browser and Node.js. Industry standard API mocking for JavaScript.
Mock Service Worker is an API mocking library that allows you to write client-agnostic mocks and reuse them across any frameworks, tools, and environments.
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A modern data client for React & tRPC
Inspired by Relay and GraphQL, fate combines view composition, normalized caching, data masking, Async React features, and tRPC's type safety.
A framework for finding JavaScript memory leaks and analyzing heap snapshots. Analyzes JavaScript heap and finds memory leaks in browser and node.js.
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✅ ESLint plugin to enforce the JavaScript Baseline.
Default to the Web Platform Baseline, the cross‑browser compatibility standard. Ship code that works for everyone.
A purely functional expression language for No-Code tools. A simple, well-designed, portable, and safe data expression language.
Elo compiles to JavaScript, Ruby, and SQL. Built for No-Code tools where non-technical users need to manipulate data easily and safely.
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OpenWorkers is an open-source runtime for executing JavaScript in V8 isolates. It brings the Cloudflare Workers programming model to your own infrastructure.
smooth squircle corners for HTML elements.
Monoco is a tiny JavaScript library that adds squircles (smooth corners) and other corner types to html elements.
🔧 A collection of essential design pattern examples in JavaScript 🧰
A collection of essential design patterns for software development using practical examples, such Singleton, Factory Method, Observer, and more, to help developers write more efficient and maintainable code.
Nostalgist.js is a JavaScript library that allows you to run emulators of retro consoles like NES and Sega Genesis, within web browsers.
MicroQuickJS (aka. MQuickJS) is a JavaScript engine targetted at embedded systems. It compiles and runs JavaScript programs using as little as 10 kB of RAM. The whole engine requires about 100 kB of ROM (ARM Thumb-2 code) including the C library. The speed is comparable to QuickJS.
Universal visualizer and analyzer for JavaScript and CSS. Compatible with most bundlers and frameworks.
Sonda is a universal bundle analyzer and visualizer. It generates an interactive HTML report that is more accurate and detailed than some alternatives. The accuracy is achieved by analyzing source maps and showing the size of each module after tree-shaking and minification.
Complete media toolkit.
Pure TypeScript media toolkit for reading, writing, and converting video and audio files, directly in the browser.
A JavaScript library for reading, writing, and converting video and audio files. Directly in the browser, and faster than anybunny else.
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The JavaScript Oxidation Compiler.
A collection of JavaScript tools written in Rust.
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A spreadsheet where formulas also update backwards.
BIDICALC is a bidirectional calculator, a spreadsheet where formulas also update backwards.
A GraphQL.js validation rule for limiting the depth (including list depth) of GraphQL operations
The ultimate Object Relational Mapper for Node.js, Bun and Deno, offering seamless integration with a variety of popular databases. Orange ORM supports both TypeScript and JavaScript, including both CommonJS and ECMAScript.
A lightweight, PostgreSQL-backed job queue. Handle background jobs with ease.
DataQueue allows you to utilize your existing PostgreSQL database to process background jobs. No need for additional infra or services.
A lightweight, PostgreSQL-backed job queue for Node.js/TypeScript projects. Schedule, process, and manage background jobs with ease. Perfect for web apps (Next.js, etc.) deployed to serverless platforms like Vercel, AWS Lambda, etc.
🗄 Zero dependency streaming tar parser and writer for every JavaScript runtime. Built with the browser-native Web Streams API for performance and memory efficiency.
Lightweight type coercion library.
Of Coerce! is a lightweight, near-zero overhead alternative to Zod and Valibot.
Unlike these libraries, Of Coerce! focuses on a single task: ensuring the data corresponds to the types.
It uses built-in JavaScript features to coerce whatever you pass to it, which makes it the fastest and the most lightweight solution (full library is 381B!).
Actor-based state management & orchestration for complex app logic. XState is a state management and orchestration solution for JavaScript and TypeScript apps.
It uses event-driven programming, state machines, statecharts, and the actor model to handle complex logic in predictable, robust, and visual ways. XState provides a powerful and flexible way to manage application and workflow state by allowing developers to model logic as actors and state machines. It integrates well with React, Vue, Svelte, and other frameworks and can be used in the frontend, backend, or wherever JavaScript runs.
JavaScript Iceberg Client.
Icebird is a library for reading Apache Iceberg tables in JavaScript. It is built on top of hyparquet for reading the underlying parquet files.
The open protocol for real-time sync to client applications.
HTTP-based durable streams for streaming data reliably to web browsers, mobile apps, and native clients with offset-based resumability.
Durable Streams provides a simple, production-proven protocol for creating and consuming ordered, replayable data streams with support for catch-up reads and live tailing.
A JavaScript toolkit that saves you time and scales with your development process. Provides everything you need to build a Web app. Language utilities, UI components, and more, all in one place, designed to work together perfectly.
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What happens when you take an XKCD joke too literally.
CLI tool that renders package dependencies as physical tower structures. Supports PyPI, npm, and crates.io with optimal crossing minimization.
Unterminated Block Parsing.
Remend is a lightweight, standalone preprocessor that completes incomplete Markdown syntax.
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True offline-first sync for modern apps—without vendor lock-in.
🔄 A powerful, type-safe sync engine for building real-time collaborative applications. Local-first, CRDT-based, with zero-config offline support.
A tiny, zero-dependency effect system for writing pure, testable JavaScript without mocks.
Pure Effect is a tiny, zero-dependency effect system for writing pure, testable JavaScript without mocks.
It implements the "Functional Core, Imperative Shell" pattern, allowing you to decouple your business logic from external side effects like database calls or API requests. Instead of executing side effects immediately, your functions return Commands which are executed later by an interpreter.
A tiny library for building editable websites in Svelte.
Svedit (think Svelte Edit) is a tiny library for building editable websites in Svelte. You can model your content in JSON, render it with custom Svelte components, and (this is the kicker) site owners can edit their site directly in the layout — no CMS needed.
Svelte Plotting Framework.
The best visualizations are built with Svelte. A Svelte-native visualization framework based on the layered grammar of graphics principles.
Safely install NPM packages.
A security-focused npm installer that protects your projects from newly compromised packages.
The current sky at your approximate location, rendered as a CSS gradient.
New JavaScript engine written in Rust.
Brimstone is a JavaScript engine written from scratch in Rust, aiming to have full support for the JavaScript language.
Brimstone is a work in progress but already supports almost all of the JavaScript language (>97% of the ECMAScript language in test262). Not ready for use in production.